Optical methods are increasingly being used for the detection of disease. Near-infrared Raman spectroscopy in particular, because of its chemical specificity, is proving to be a useful tool for both disease diagnosis and the study of disease progression. Over the past decade Raman spectroscopy has been applied to many diseases and biological problems and there have been many advances in-vitro. More recently there have been reports of in-vivo work that however have either been confined to studies of skin or other easily accessible organs, or have used optical fiber configurations that require collection times that are unreasonably long for practical clinical use. The majority of applications require remote sampling via optical fibers, and the size of the probe and fiber bundle is strictly limited by the application. A particular example that current commercial systems cannot provide is the ability to evaluate atherosclerotic lesions in-vivo in real-time, through an angiographic catheter, thus aiding cardiologists in directing the most appropriate treatment in each individual case. These objectives have not been fulfilled by current systems.
In addition, prior art probes for remote Raman sensing, using several different methods for filtering out the fiber spectral background, either exhibit extremely low optical throughput or are too bulky to be used intravascularly. A problem with the prior art designs includes having a 4 cm long stiff tip that prohibits their incorporation into transcutaneous catheters for accessing the coronary arteries. Secondly, in data collected with these probes, a considerable component of the fiber Raman spectrum still remains. Further, data collection times on the order of 30 seconds or longer are typically required for collection of signals with an acceptable signal to noise ratio (SNR).
A need still exists for improved systems and methods which include probes for, for example, Raman spectroscopy that are sized for applications in medicine and provide an improved spectral signature from tissue.